Alloy



Patented Mar. 18, 1930 UNITED STATES PATENT OFFICE.

PIERRE BERTHELEMY AND HENRY DE MONTIBY, OF PARIS, FRANCE I ALLOY No Drawing. Application filed Augu lt 9, 1927, Serial No, 211,849, and in France May 20, 1927.

It has already been proposed to incorporate cadmium into aluminium and its alloys, this incorporation enabling an inoxidizable metal or alloy to be obtained. It is, however,

known that, with the processes actually employed it is impossible to achieve a homogeneous incorporation of the cadmium; furthermore if during preparation a considerable quantity of cadmium is added to the metal, only slight traces of cadmium irregularly distributed in the mass are found when the operation is completed. his stated that the cadmium forms waves in the metal; Brinell tests carried out on samples of such a metal show relatively soft spots at thepoints where the cadmium is located.

The present invention has for its object to provide a process which enables the incorporation of any quantity of cadmium into aluminium and its alloys, in such a manner that the cadmium introduced is distributed in a perfectly homogeneous manner throughout the mass and the cadmium content of the resulting metal can be predetermined with absolute precision.

The process according to the invention is characterized substantially by the incorporation in all alloys having an aluminium base of cadmium in the presence of magnesium. The presence of the magnesium has the effect of ensuring the homogeneous distribution of the cadmium in the mass and the incorporation in said mass of an. exactly proportioned quantity of cadmium. We have proved by experience that this method of operation has the effect of radically eliminating the well known disadvantages of incorporating magnesium alone with aluminium or its alloys (it is known that magnesium alone renders the aluminium more oxidizable) Whereas in the known processes not more than 0.20% of cadmlum can be incorporated, with the process according to the present invention it is possible to incorporate any desired quantity of cadmium; it is this which enables an inoxidizable metal to be obtained.

By way of example a method of operation will now be described which applies to an aluminium alloy of the kind described in 60 French Patent 610,464. The metal obtained,

as will be shown, can be cast in pieces, in sand or chilled. It may also be rolled, drawn and wiredrawn; it can be soldered with a soldering iron or welded by autogeneous or electric arc welding and it can be forged.

In a crucible lined with magnesia, a certain quantity of aluminium is smelted; when the mass is in fusion cupro-tungsten, cuproferro-silicon, and cupro-manganese are added in the order of their respective fusing points and the bath is then covered with a light layer of deoxidizing powder the composition of which is indicated in the above mentioned patent. When the mass is again fused new ingots of pure aluminium are added which have been preliminarily heated in a furnace, in order to avoid a sudden cooling of the mass contained in the crucible. The temperature of the molten alloy must be maintained at a suitable value; the optimum temperature is 640 Centigrade. Stirring and skimming is then effected by usual methods. 0

It is at this time that the final addition is effected, i. e. that part of the operation intended to produce inoxidizability.

This final addition may consist either-of a mixture of cadmium, aluminium and magnesium, or more simply, a mixture of magnesium and cadmium. For this final addition it is the magnesium which renders possible the incorporation of cadmium in large quantities in any alloy the basis of which is aluminium, the cadmium being uniformly distributed in the mass of the final product.

By the process according to this invention a metal is obtained which is absolutely inoxidizable in sea water, saline air and soft water; terrazolith (oxychloride of magnesium) and hyposulphite salts have no injurious effect on aluminium alloys treated according to the invention.

On the other hand, the cadmium incorporated according to the process which forms the object of the invention prevents the formation of cracks and blow holes which always form in light alloys of high resistance, and which are often an obstacle to the use, in foundry work, of the alloys in question. On account of the perfectly homogeneous distribution of the cadmium in the mass of metal,

faultless castings can be obtained, and the metal can be made homogeneous to an extent hitherto unknown in the aluminium i11- dustry. This enables the metal thus obtained to be used for making parts which come into direct contact with petrol, benzine, etc.

For producing an alloy having an aluminium base of the kind which we have previously described, the operation is effected in several phases, in the following manner:

I. An alloy is made rich in cupros cupro-manganese, cupro-ferrosilicon, cuprotungsten, cupro-molybdenum, cupro-nickel, cupro-cobalt, cupro-titaniuun, cupro-vanadium, cupro-uranium, and the like).

II. This rich alloy (for the preparation of which the proportion of each ingredient has been chosen according to the characteristics which it is desired to give to the final metal) is incorporated in a mass of aluminium.

III. The metal is stirred and skimmed by usual methods.

IV. Finally an alloy of aluminium, cad- ;nium and magnesium is added; this is stirred energetically and the metal allowed to settle during half an hour. It only remains to cast same. Tests have shown that the magnesium causes the cadmium to be incorporated in the final aluminum alloy in the form of a uniformly distributed solid solution.

When it is desired to obtain an inoxidizable metal, 2% of cadmium is incorporated, this quantity being sufficient to create the comnlete inoxidizability of the mass. It should, however, be understood that, in other alloys comprising for example a considerable quantity of magnesium, it is also easy, in applying the process according to the invention, to

introduce any quantity of cadmium. These cadmium contents are given solely by Way of indication; they cannot however apply in the case of light metals the specific gravity of which does not exceed 3.

In determining the quantity of cadmium to be incorporated the mechanical properties desired for the finished metal should also be borne in mind; it is known, for example, that cadmium considerably reduces the capacity for elongation.

In an alloy of aluminium such as that described in the above mentioned French Patent 610,464, the incorporation of 2% cadmium enables the said metal to be rolled, drawn or wiredrawn, with 22 to 24% elongation and a tensile strength of 40 to 44 kilos, an apparent limit of elasticity of 36 kilos, and a Brinell hardness of 160.

In the production of bronzes, the alloy constituting the final addition should be analloy of tin and cadmium with traces of magnesium. In aluminium bronzes a final addi-- tion is made of aluminium and cadmium contaming always traces of magnesium; the

operation is carried outin the manner indicated above.

Whatever alloy is treated according to the invention the result is always the same. The process permits the incorporation of a'quantityof cadmium sufiicientto ensure a perfeet inoxidizability and to obtain perfect homogeneous distribution of the said cadmium in the mass, whercas in processes used hitherto it was impossible to incorporate more than 0.20% cadmium, this quantity being absolutely insufficient to produce inoxidizability, especially in salt water or saline air. Furthermore, even in such reduced quantities the cadmium was irregularly distributed in the mass.

It is to be noted that nickel and cobalt, if they are not associated with the cadmium in the alloys of aluminium, give no resistance to corrosion.

What we claim is 1. In the art of introducing cadmium into an alloy having an aluminum base, that step in the art which consists in adding the cadmium intermixed with alminum and magnesium so that the cadmium is incorporated in the alloy in the form of a uniformly distributed solid solution, the proportion of cadmium in the final alloy being not less than 2%.

2. In the art of introducing cadmium into an aluminum alloy, that step in the art which consists in substantially simultaneously introducing cadmium and magnesium into the molten aluminum alloy, and stirring the ingredients while preventing the temperature from exceeding 640 C., the proportion of cadmium in the final alloy being not less than 2%.

In testimony whereof we have signed our names to this specification.

PIERRE BERTHELEMY. VTE. HENRY DE MONTBY. 

